Control system



. A. L. HARVEY.

CONTROL SYSTEM. APPLICAHON FILED 1AN.25. 1919.

Patented Nov. 14, 1922.

WITNESSES:

INVENTOR A/fierl L Han 8] Q BY 7 MM @I LK MW Patented Nov. 14, 1922.

UNITED STATES PATENT OFFICE.

ALBERT L. HARVEY, OF WILKINSBUBG, PENNSYLVANIA, ASSIGNOR TO wns'rme;

HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VANIA.

' Application filed January 25, 1919.

To all whom it may concern: Be it known that'I, ALBERT L. HARVEY, a citizen of the United States, and a resident of Wilkinsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Control Systems, of which the following is a specilication.

My invention relates to u'iotor-control systems. The object of my invention isto provide an improved motor-control system which shall beEespecially useful at times when the voltage of the'source of power for the motor falls below a predetermined value. "-My inventionfinds particular application in connection with motors, such as fan and pump motors, which are employed in places that-are not easily accessible, such as mines,

where frequent visits are inconvenient and the constant presence of an attendant is undesirable. According to my invention, upon the failure of voltage, instead of the motor becoming disconnected from the line, the accelerating resistor is automatically reinserted into circuit. Upon the return of power to the line, the motor is automatically restarted, with the accelerating resistor in series therewith, so as to protect the motor windings from injury. A relay is provided for protectin the motor from the elfects of overload conditions. I

The single figure of the accompanying drawing is a diagrammatic view of circuits and apparatus illustrating my invention.

A motor having an armature 1 and a shunt field-magnet winding 2, is connected between line conductors 3 and 4. Although I have illustrated a shunt motor, acompound motor or a series motor may be employed, if desired. An accelerating resistor 5 is connected in series with the armature 1 and a resistor may be provided in the circuit of the shunt field-magnet winding 2.: A contactor 7 having an energizing coil 8, the circuit of which may be closed by a pushbutton 9, is adapted to close the circuits of the armature 1 and the field-magnet winding 2. A plurality of contactors 10, 11, 12 and 1.3 are provided for short-circuiting the re. sistor 5, the contactorshaving actuating coils 14, 15, 16 and 17', which are respectively controlled by-current-limit relays 18, 19, 20 and 21, that are respectively mechanically CONTROL SYSTEM.

Serial No. 273,037.

connected to the contactors 7, 1O, 11 and 12. An overload relay 24 is provided, having an actuating winding 25 in series with the armature .1 for opening the circuit of the coil 8 when the current traversing the armature 1 cxceeds'a redetermined value.

,A low-"0 tage relay 26, having an actuating coil 27 in series with an adjustable resistor 28, controls the circuit of the coil 14 of the contactor 10. I I

The operation is as follows: When the push-button 9 is depressed, a circuit is established which extends from the line conductor3, through the coil 25,- the overload relay 24, the coil 8 and the push-button 9, to the line conductor 4. The contactor 7 is thereupon closed to establish the arn-mture circuit which extends from the line conductor 3, through the coil 25, contactor 7, the energizing coil of the current-limit relay 18, the resistor 5, and the armature 1 to the line conductor 4. A circuit is also established for the shunt field-magnet winding from the contactor 7 by way of a conductor 22. through the shunt field-magnet winding 2 to. the line conductor 4. The motor is thereupon started at slow speed. A circuitis established also fromthe line conductor 3, through the coil 25, the overload relay 24, the coil 27, the resistor 28 and the pushvbutton 9, to the line conductor 4. This will effect vthe closing of the low-voltage re,- lay 26. t

The closing of the contactor T releases the current-limit relay 18, which will remain open so long as the current traversing the armature circuit exceeds a predetermined value. Upon the closing of the relay 18, a circuit will be established from the line conductor 3, through the coil 25, the overload relay24, the current-limit relay 18, the actuating coil 14,7the low-voltage relay 26 and the push-button 9, to the line conductor 4. The contactor 10 will thereupon be closed. whereupon the motor-circuit will extend fromthe line conductor 3 through the coil 25, the contactor '7, the coil of the relay 18, by way of a conductor 23. the contactor 10, the coil of the current-limit relay 19, a large portion of the resistor 5 and the armature 1,

to the line conductor 4. A portion of the rej sistor 5 is thus short-circuited, causingan increase in the motor speed. \Vhen thecu'rrent-limit relay 19, which is released upon the closing of the contactor llO, closes in ac cordam-e with current conditions. a circuit will be established from the line conductor 3, through the coil 25, the overload relay 24:, the current-limit relay 19, the coil and the push-button 9, to the line conductor 4t. The cont-actor 11 will thereupon be closed to short-circuit an additional portion o1 the resistor 5. The armature circuit will now extend from the contactor T, which is connected to the line conductor 3 through the coil of the relay 18, the conductor 43,, the contactor 10, the coil oi? the relay 19, the contactor 11, the coil of the relay 20, a portion of the resistor and the armature l, to the line conductor l. In similar fashion, the contactors ilQ and l3 will close, upon their actuating coils lb and 17 l'iecoming energized, tollowing the closing of the currentlimit relays 20 and 21. The coils of the current-limit relays 18, 11*,20and 21 will become tie-energized with the closing of the contactor 13, the motor circuit GXt-Gl'ltllff from theline conductor 3, through the coil 25, the contactors '7 and 13 and the armature l to the line conductor The motor will then operate at normal speed. It will be notedthat the puslnbutton 9 adapted to open all the control. circuits. It may, if desired, be placed atthe point '6, in which eventit would. open the circuit oiv the coil 8 only. The push-button may control any desired number of the control circuits. When the voltage of the source falls to a predetermined value, as, for example, of normal voltage, the relay 26 opens to open the circuit of the coil 14, thereby to cause the opening of the contactor 10. The current-limit relay 19 will thereupon be automatically opened by its controllingspring; to cause the opening ofthe circuit 01' the coil 15, which, in turn, will cause the opening of the cont-actor 11. In similar manner, the coils l6 and 17 will become de-energized, and, upon the opening oi? contactor 13, the resistor 5 is inserted in the motorcircuit. The motor will thereupon continue to operate, but at slow speed.

lit desired, the coils 14, l5, l6 and i? may all be placed under the direct control oil the low-voltage relay 2-6, in which case, the contactors 10, 11, 12 and 13 would be opened together under low-voltage conditions.

Upon the voltage rising, say to the coil 27 will eli'ect the reclosing oi the relay 26, which, in turn, will cause again the energization of the coil l l, whereupon the con tactor 10 will become reclosed to effect again the short circuiting of a portion of the resistor 5. The relay l9, thereupon reclosing' when the current drops to a predetermined value, will cause the reclosing, oil? the contact-or 11, the operation of short-circuiting the resistor aim-11;;- thc san'ie as that above described; I

The value of the voltage at which the re lay will operate may be changed by suitably adjusting. ai'itomatically or mani'lally, the resistor When the current traversing the motor circuit exceeds a predetermined value, tl'e coil 25 will effect the opening of the overload relay 24.- and this, in turn, will cause the de-energization of the coil 8 to cause the openin or the contactor 7. The motor will thereupon be disconnected from the line condoctors 3 and l. Upon the reclosing of the overload relay 24;, assuming that the pushbutton 9 remains closed, the circuit of the coil 8 will become recloscd to cause the reclosing of the contactor 7 and the reconnecting of the motor to the line conductors .3 and i. It will be noted that the relay 9A is etched in its open position until released manually. This arrangement prevents intermittent operation or pumping in case of continuous overload. 1

The above-described operations take place automatically, in accordance with changes in line voltage and the, current traversing the motor circuit. It is not necessary that the control apparatus be readjusted after voltage failure. The push-button 9 may be located at some distant point and the opera tion of this button will effect the closing or the openingof the motorcircuits, as desired.

Many modifications (will suggest then'iselves to those skilled in the art and I desire, therefore, thatmy invention be construed broadly except in so ttarv as limitations may be specifically imposed in the appended claims.

I claim as my invention:

1.. The combination with an electric motor having a resistor associated therewith and a source of energy for said motor, of means comprising a low-voltage relay for inserting said resistor into circuit with said motor when the voltage of said source falls below a predetermined value, while the circuit. or lilo said motoris maintained, and for ShOl'il-Cll' cuiting said resistor when the oltage of said source rises above a. predetermined value.

2. The combination with an electric motor having an armature, a resistor in series therewith, a plurality of electromagnetic switches for short-circuiting said resistor and having actuating coils and a source of energy for said motor, of a relay operable ata predetermined minimum value of the voltage of said source for el'lectinp; the opening of the circuits of said coils, the circuit of said motor being uninterrupted.

'3. The combination with an electric motor having an armature, a resistor in series therewith a switch for short-circuiting said resistor andv having; an actuating coil and a source of energy tlfor said motor, of a relay having an actuating coil connected to said source for controlling the circuit 0'! said 130 resistor-switch coil and means whereby said controlling switch coil causes the closing of said controlling switch when the voltage of said source is above a predetermined value and causes the opening of said controlling switch when the voltage of said source is below a second predetermined value, and

means for maintaining the closure of the motor circuit while said cont-rolling switch is open.

ALBERT L. HARVEY. 

